Association of smoking with the efficacy of continuous glucose monitoring in type 1 diabetes: A propensity score-matched cohort study

Abstract

Introduction

Smoking affects glycemic control in individuals with type 1 diabetes (T1D); however, its impact in the era of continuous glucose monitoring (CGM) has not been thoroughly studied.

Materials and methods

A retrospective cohort study was conducted at two centers, involving 405 T1D patients treated with multiple daily insulin injections and using CGM. The patients were matched using propensity scores based on sociodemographic and clinical characteristics. HbA1c levels were analysed before and after a 2.2-year follow-up period. The analysis was performed using mixed linear regression and multivariable conditional logistic models.

Results

The sample included 135 smokers and 270 non-smokers, with a mean age of 47.6 years, and 50.1% were women. Both groups had a similar baseline HbA1c of 8.0 (1.5%). After follow-up, non-smokers reduced their HbA1c to 7.3 (1.1%), while smokers only reduced it to 7.7 (1.3%), 95% CI [−0.57–0.10]). The proportion of non-smokers achieving HbA1c <7% increased from 25% to 38.1%, 95% CI [0.14–0.36, whereas smokers showed no change (25.9%, 95% CI [−0.13–0.21]). Smoking was independently associated with a higher risk of not achieving HbA1c <7%, despite CGM use (odds ratio 1.89, 95% CI [1.13–3.17].

Conclusion

Smoking limits the glycemic control benefits of CGM in individuals with T1D. It is crucial to include smokers in clinical trials and to develop strategies to discourage smoking in this population to maximise the benefits of diabetes technology.